Cytomegalovirus (CMV) infection in utero is an important cause of central nervous system damage in newborns. Although the virus is widely distributed in the population, about 40% of women enter pregnancy without antibodies and thus are susceptible to infection. About 1% of these women undergo primary infection in utero. Classical cytomegalic inclusion disease is rare; however, a proportion of the infected infants, including those who were symptom free, are subsequently found to be mentally retarded (Lancet Jan. 5, 1974, pp. 1-5).
Preliminary estimates based on surveys of approximately 4,000 newborns from several geographical areas indicate that the virus causes significant damage of the central nervous system leading to mental deficiency in at least 10%, and perhaps as high as 25%, of infected infants. Assuming that about 1% of newborn infants per year excrete CMV and that about one fourth of those develop mental deficiency, in the United States this means approximately 10,000 brain-damaged children born per year. This is a formidable number, particularly in view of the ability of these children to survive (J. of Infect. Dis. 123, No. 5, 555 (May 1971)).
In view of the seriousness of the problem, research directed toward the development of an effective CMV vaccine has been stimulated in recent years. The problem for vaccination is to provide cell-mediated and humoral immunity without allowing spread of virus throughout the body of the vaccinee and without causing ill effects. The vaccine should be useful in protecting women against infection during pregnancy. Vaccination of adolescent girls should reduce the incidence of primary CMV infection in pregnancy and eliminate fetal brain damage due to this cause.